<button type="submit" title="<?php /* @escapeNotVerified */ echo __('Buy Now') ?>" id="buy-now" class="action buynow primary" data-mage-init='
{
    "Mazentop_BuyNow/js/buy-now": {
        "form": "#product_addtocart_form"
    }
}
' onclick="ga('send','event','buy now','click')">
    <span><?php /* @escapeNotVerified */ echo __('Buy Now') ?></span>
</button>